Abaixo está uma instrução que descreve uma tarefa de geração de SQL, combinada com uma entrada que fornece mais contexto sobre os esquemas de tabela disponíveis. Escreva o código SQL que responda adequadamente à solicitação
 ###Instrução: Qual classe tem menos de 12 números construídos operados pelo sul?
 ###Tabelas: CREATE TABLE attendance_at_home_games (attendance_at_home_games_id AUTO_INCREMENT PRIMARY KEY, Round VARCHAR, Date VARCHAR, Opponent VARCHAR, Score AUFC – Away VARCHAR, Attendance INT, Weekday VARCHAR) CREATE TABLE grand_slam_men's_doubles_finals:_20_16–4 (grand_slam_men's_doubles_finals:_20_16–4_id AUTO_INCREMENT PRIMARY KEY, Outcome VARCHAR, Year INT, Championship VARCHAR, Surface VARCHAR, Partner VARCHAR, Opponents VARCHAR, Score VARCHAR) CREATE TABLE fleet_details (fleet_details_id AUTO_INCREMENT PRIMARY KEY, Class VARCHAR, Operator VARCHAR, No. Built INT, Year Built VARCHAR, Cars per Set INT, Unit nos. VARCHAR) CREATE TABLE university_location_date_established (university_location_date_established_id AUTO_INCREMENT PRIMARY KEY, University VARCHAR, Location VARCHAR, Established INT, Endowment as of 2008 VARCHAR, Campus Area (acres) INT, Kiplinger's Top 100 Values VARCHAR, Enrollment as of 2008 INT) CREATE TABLE medals (medals_id AUTO_INCREMENT PRIMARY KEY, Rank INT, Nation VARCHAR, Gold INT, Silver INT, Bronze INT, Total INT)  
SELECT Class FROM fleet_details WHERE No. Built < 12 AND Operator = southern